C(19,12,2) = 4

Method of Construction: simple construction: added element to c(v-1,k-1,t) covering

Lower Bound: Schonheim

  1  2  3  4  7  8 10 12 13 15 16 19
  1  3  4  6  7  8 10 12 13 14 17 19
  1  3  4  5  7  8  9 10 11 12 18 19
  2  5  6  9 11 13 14 15 16 17 18 19